Method of transmitting or receiving a data packet in packet data communication system using hybrid automatic repeat request

ABSTRACT

A method of transmitting/receiving a packet using a hybrid automatic repeat request in the mobile communication system is disclosed. The packet data transmitting method includes transmitting at least one sub packet divided from plurality of encoded packets generated by repeating a bit stream that is made by encoding information desired to be transmitted with 1/5 rate turbo encoder, and transmission start point information of the sub packet through the sub packet identifier field on the accompanying control channel.

This application is a continuation of U.S. application Ser. No.10/103,753, filed Mar. 25, 2002, now U.S. Pat. No. 7,346,037, whichpursuant to 35 U.S.C. § 119(a) claims the benefit of the KoreanApplication Nos. P01-15738, P01-17139, and P01-21830 filed on Mar. 26,2001, Mar. 31, 2001 and Apr. 23, 2001, which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile communication system, and moreparticularly, to a method of transmitting or receiving a data packet inpacket data communication system using a hybrid automatic repeatrequest.

2. Discussion of the Related Art

Generally, a hybrid automatic repeat request (HARQ) is used fortransmission of packet data in a mobile communication system.

That is, the object of the HARQ is to improve the reliability andthroughput during data transmission in the communication system bycombining an automatic repeat request (ARQ) with a forward errorcorrection (FEC).

The object of the ARQ is to improve the reliability in a manner that areceiving end requests repeat of the same information until theinitially sent information is received in the receiving end withouterror. The object of the FEC is for the receiving end to compensate forthe error occurring due to the channel environment using an errorcorrection code.

If the channel environment is good and the error occurring frequency ofthe given information is low, only the use of the ARQ will suffice forthe reliability.

However, if the channel environment gets worse, the error occurringfrequency of the given information becomes greater, and thus thefrequency of repeat request also becomes greater.

This deteriorates the throughput of the system. Thus, it has beenproposed to use both the ARQ and the FEC, which is called the HARQ.

As a kind of the HARQ, there is a method that uses an incrementalredundancy.

According to this method, a transmitting end first transmits informationencoded with a high coding rate to a receiving end, encodes theinformation with the coding rate lowered whenever the repeat request isreceived from the receiving end, and then transmits only the additionalredundancy bits to the receiving end. The receiving end combines thereceived redundancy bits with the previously sent information to decodethe information.

These additional redundancy bits are bits added for error correction ordetection of the previously transmitted data packet.

To do so, the receiving end can obtain the gain according to thecombining. Also, since the combining coding rate of the packet data isgradually reduced whenever the repeat is performed, the transmitting endcan adaptively give the redundancy to the data packet according to thechange of the channel environment.

Currently, in a high data rate (HDR) mobile communication system, theincremental redundancy of the HARQ, particularly a synchronousincremental redundancy (SIR) is used.

According to the SIR method, as shown in FIG. 1A, information to betransmitted is encoded and repeated to construct one packet, and thenthe data packet is divided into sub packets of a fixed size fortransmission.

Specifically, the transmitting end transmits a sub packet among subpackets that constitute a data packet. If the receiving end performsdecoding of the transmitted sub packet without error and transmits anacknowledgment (ACK) to the transmitting end, the transmitting endtransmits no further sub packet.

If the receiving end fails to perform the decoding of the transmittedsub packet and transmits a non-acknowledgment (NACK) to the transmittingend, the transmitting end transmits the next sub packet.

Meanwhile, in order to heighten the transmission rate in the changingchannel environment, it is advantageous to change the length of therespective sub packets according to the changing channel environment.

Accordingly, in order to implement this, a method that uses a variablesub packet length has been proposed as shown in FIG. 2A.

During the process of dividing a data packet into several sub packetsand transmitting the sub packets, this method enables the transmissionof the respective sub packets to be performed with different sub packetlengths according to the channel environment.

At this time, there is provided a control channel for notifyinginformation on the length of the sub packet, sub packet identifier (ID),etc.

If the transmitting end transmits the packet data to the receiving endthrough the above-described process, the receiving end extractsinformation on the sub packet through the control channel to receive thesub packet.

Then, the receiving end performs the decoding of the data packet byconcatenating/combining the received sub packet with the data packetpreviously sent from the transmitting end using the extractedinformation.

In case of using the sub packets of the fixed length as shown in FIG.1A, the length of all the sub packets is fixed, and thus the receivingend can grasp the transmission start point of the currently received subpacket if it knows the order of the sub packets even when it cannotreceive any sub packet. Thus, it can perform the decoding byregenerating the packet with other sub packets (or even with only onesub packet) as shown in FIG. 1B.

Thus, if there is information on the order of the sub packet currentlytransmitted, the receiving end can recognize the transmission startpoint of the sub packet. In case of using the SIR method in the HDRsystem, the receiving end can always recognize information on when itsown sub packet is received after the first sub packet is received, andthus does not require other control information in the event that thereceived sub packet is not the fifth sub packet. However, in case ofusing an asynchronous incremental redundancy, the transmission time ofthe next sub packet may randomly change even if the transmission time ofthe first sub packet is determined, and thus all the sub packets shouldbe transmitted to the receiving end along with the information on thesub packet ID and the sub packet length that is the control informationon the sub packet. In case that the length of the respective sub packetis fixed, the receiving end can recognize the transmission start pointof the respective sub packet even if the transmitting end just transmitsthe sub packet IDs in order.

However, according to the method that uses the sub packets of thevariable length as shown in FIG. 2A, the length of the sub packet ischanged whenever the sub packet is transmitted, and thus if the controlchannel that includes the sub packet information is not received, thestart point of the data packet cannot be recognized only through therespective sub packet ID.

That is, it cannot be recognized where the currently received sub packetstarts. For this reason the variable length type method cannot decodethe data packet even if only one sub packet is missing.

Specifically, if a sub packet 2 is not received and a sub packet 3 isreceived, there is no information on the previous sub packet 2 duringthe process of concatenating the sub packet 1 and the sub packet 3, andthus it cannot be recognized of which type between two types as shown inFIGS. 2B and 2C the sub packet 3 is received.

In the sequential transmitting method wherein the transmission of thenext sub packet starts at a position where the transmission of theprevious sub packet ends, if the receiving end misses even one subpacket, it cannot recognize the transmission position of the incomingsub packet after the missing sub packet, and thus the decoding cannot beperformed.

To solve the above-described problem, a method is used as follows. Thatis, in transmitting variable sub packets, each sub packet is transmittedfrom the fixed start position in the encoded packet to the receivingend, and the information on the length and the starting position of thesub packet is transmitted to the receiving end through the controlchannel. The receiving end extracts the information on the sub packetthrough the control channel, and performs the decoding byconcatenating/combining the received sub packet with the previouslyreceived sub packet using the extracted information.

However, in case of using this method, a certain portion in the encodedpacket may be repeatedly transmitted, while another portion may not betransmitted, resulting in that the coding gain according to the HARQcannot be obtained sufficiently.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method oftransmitting a sub packet of a variable length using a hybrid automaticrepeat request in the mobile communication system that substantiallyobviates one or more problems due to limitations and disadvantages ofthe related art.

An object of the present invention is to provide a method oftransmitting a sub packet of a variable length using a hybrid automaticrepeat request that enables a receiving end to perform decoding of thedata packet by regenerating transmitted sub packets even if any subpacket is missing during transmitting/receiving of the sub packets.

Another object of the present invention is to provide a method oftransmitting a sub packet of a variable length using a hybrid automaticrepeat request (HARQ) that can increase the coding gain according to theHARQ.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod of transmitting a data packet in packet data communication systemusing hybrid automatic repeat request includes transmitting at least onesub packet divided from plurality of data packets generated by repeatinga bit stream that is made by encoding information desired to betransmitted with ⅕ rate turbo encoder, and transmission start pointinformation of the sub packet through the sub packet identifier field onthe corresponding control channel.

In another aspect of the present invention, a method of transmitting adata packet in packet data communication system using hybrid automaticrepeat request includes generating plurality of data packets byrepeating a bit stream that is made by encoding information desired tobe transmitted with ⅕ rate turbo encoder, and dividing the plurality ofdata packets into at least one sub packet. Here, the sub packets aredivided according to transmission start points determined according to arule made between a transmitting end and a receiving end. Thetransmitting end informs the transmission start point through a controlchannel using a sub packet identifier, and transmits the correspondingsub packet to the receiving end through a data transmission channel,starting from the transmission start point.

Preferably, the transmission start point of the respective sub packet isdetermined according to the number of code symbols of the correspondingsub packet and a corresponding sub packet identifier. Here, the possiblestarting points for present sub packet transmission in the data packetare calculated as taking modulo 5N operation on the products between thenumber of code symbols of the corresponding sub packet and thecorresponding sub packet identified, where N represents the length ofinformation bits of the data packet. Here, the number of code symbols isdetermined according to the number of slots through which the sub packetis transmitted, data rate, modulation type, and the number of Walshcodes available for the sub packet transmission.

Preferably, the selection of the sub packet identifier to be presentlytransmitted is performed in a manner that the sub packet identifierhaving a maximum coding gain among the remaining sub packet identifiersexcept for the sub packet identifier for representing an initialtransmission position is selected.

Preferably, the method further includes the steps of mapping thetransmission start points at equal intervals in the data packet, andtransmitting a certain sub packet, starting from one of the mappedtransmission start points.

Preferably, the method further includes the steps of mapping thetransmission start points at unequal intervals in the data packet,mapping more transmission start points on a position of the data packetwhere the bit stream having high importance is located, and mapping lesstransmission start points on a position where the bit stream having lowimportance is located, and transmitting a certain sub packet, startingfrom one of the mapped transmission start points.

Preferably, the method further includes additionally transmittingthrough the control channel information on whether the sub packetcorresponding to the transmission start point information is the subpacket of a new packet or the successive sub packet of the previouspacket.

Preferably, among combinations composed of predetermined numbers ofbits, two combinations represent the initial transmission start pointinformation of the sub packet, and the remaining combinations representother transmission start point information. Here, one of the twocombinations that represent the initial transmission start pointinformation represents the initially transmitted sub packet in thepacket, and the other represents the successive sub packet of thepreviously transmitted sub packet.

In still another aspect of the present invention, a method of receivinga data packet in packet data communication system using hybrid automaticrepeat request includes receiving through a data transmission channel atleast one sub packet divided from plurality of data packets generated byrepeating a bit stream that is made by encoding information desired tobe received with ⅕ rate turbo encoder, receiving through a controlchannel transmission start point information of the received sub packetin the data packet, and regenerating the data packet according to thecorresponding transmission start point information of the sub packet.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1A is a view illustrating the construction of a data packet havingsub packets of a fixed length according to a conventional hybridautomatic repeat request method.

FIG. 1B is a view illustrating the construction of the data packet ofFIG. 1A wherein a certain sub packet of the fixed length is missing.

FIG. 2A is a view illustrating the construction of a data packet havingsub packets of a variable length according to a conventional hybridautomatic repeat request method.

FIGS. 2B and 2C are views illustrating the construction of the packet ofFIG. 2A wherein a certain sub packet of the variable length is missing.

FIGS. 3A and 3B are views explaining examples of a sub packettransmitting method according to the present invention.

FIG. 4A illustrates a packet having sub data and blocks for generatingthe data packet in case that information in the data packet does nothave a positional reliability according to the present invention.

FIG. 4B illustrates a data packet having sub packets and blocks forgenerating the data packet in case that information in the data packethas a positional reliability according to the present invention.

FIG. 5A is a view illustrating transmission intervals of respective subpackets in case that start points in a encoded data packet are dividedat equal intervals according to the present invention.

FIG. 5B is a view illustrating transmission intervals of respective subpackets in case that start points in a encoded data packet are dividedat unequal intervals according to the present invention.

FIG. 6 is a view illustrating an encoded packet generated byregenerating the transmitted sub packets in a receiving end according tothe present invention.

FIG. 7 is a view illustrating transmission intervals of respective subpackets of a variable length according to a hybrid automatic repeatrequest method according to the present invention.

FIGS. 8A and 8B are views illustrating an example of an AIR typetransmitting and restoring method according to the present invention.

FIGS. 9A and 9B are views illustrating another example of an AIR typetransmitting and restoring method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Now, the features and effects of the data packet transmitting/receivingmethod according to the embodiments of the present invention will beexplained with reference to the accompanying drawings.

First Embodiment

The first embodiment of the present invention provides a method capableof decoding received sub packets even if a receiving end fails toreceive any one of the sub packets by fixing transmitted positions ofthe respective sub packets in a packet when transmitting the sub packetshaving a variable length.

FIGS. 3A and 3B are views explaining examples of a sub packettransmitting method according to the present invention.

In FIGS. 3A and 3B, starting points are positioned at equal intervals.

In FIG. 3B, the same information in the data packet may overlap eachother over two sub packets.

Referring to FIGS. 3A and 3B, when transmitting the sub packets, thetransmitting end transmits the respective sub packet, starting from aproper position selected among the previously determined sub packettransmission start points.

First, the transmitting end determines several transmission start pointspositioned at equal intervals to transmit the sub packets.

Thus, the sub packet ID information that the transmitting end transmitsthrough the control channel does not mean information on the order ofthe sub packets presently transmitted by the transmitting end, but meansthe start point information for informing from which transmission startpoint among the several start points promised between the transmittingend and the receiving end the transmission of the present sub packetstarts.

That is, the transmitting end informs that the transmitted sub packet isa sub packet that starts at a certain time point among the promisedtransmission time points P1, P2, P3, and P4.

As described above, the transmitting end transmits the start pointinformation to the receiving end, and thus the receiving end canrecognize at which position the respective sub packet is located in thedata packet even if the previous sub packet is missing.

Accordingly, even in case that any sub packet is missing, the receivingend can receive other sub packets except for the missing sub packet,regenerate the data packet by concatenating or combining the receivedsub packets, and decode the regenerated packet.

Two methods of mapping the transmission start points of the sub packetsin the encoded packet may be considered.

One is a method having start points at equal intervals. In case that allthe information in the data packet have the same importance, thetransmission start points of all the sub packets are mapped at equalintervals in the data packet irrespective of the importance of theinformation.

The other is a method having start points at unequal intervals. If thestart points are mapped at equal intervals in case that the informationin the encoded packet have different importance according to theirpositions, the information having a high importance may not betransmitted to cause a loss.

Accordingly, in order to heighten the probability that the informationat the position of a high importance, the transmission start points aremapped at unequal intervals by mapping more transmission start points onpositions of a high importance in the data packet.

The data packet constructions according to the present invention whereinthe transmission start points are mapped in two cases are shown in FIGS.4A and 4B.

FIG. 4A illustrates a data packet having sub packets and blocks forgenerating the data packet in case that the information in the packetdoes not have a positional reliability according to the presentinvention.

FIG. 4B illustrates a packet having sub packets and blocks forgenerating the data packet in case that the information in the datapacket has a positional reliability according to the present invention.

Referring to FIGS. 4A and 4B, in a system provided with a mother coderhaving a code rate of ⅕, a turbo encoder 101 provides 5 kinds of outputsX, Y0, Y0′, Y1, and Y1′.

Here, X denotes information bits, and Y0, Y0′, Y1, and Y1′ denoteredundancy signs added to the information bits.

A reordering/interleaving block 102 receives the bit stream outputted asabove, and generates encoded packets. A repetition block 103 receivesthe encoded packets, and generates the data packet.

At this time, it is assumed that the encoded packets are infinitelyrepeated, and the transmitting end successively transmits the subpackets until the receiving end decodes the encoded packets withouterror. Also, it is assumed that the data packet is divided into aplurality of sub packets having a variable length.

As shown in FIG. 4A, if X, Y0, Y0′, Y1, and Y1′ are uniformlydistributed in the whole encoded packet during the interleaving, nopositional importance of the encoded packet exists.

Accordingly, in case that the transmission start points are mapped bydividing the encoded packet into four parts, and the sub packetscorresponding to the respective transmission start points are to betransmitted, the transmission start points of the sub packet in theencoded packet are mapped on the positions where the encoded packet isdivided into four parts.

FIG. 5A is a view illustrating transmission intervals of respective subpackets in case that start points in an encoded packet are divided atequal intervals according to the present invention.

As shown as (2) in FIG. 5A, the information of the respective subpackets may overlap each other.

At this time, as can be known through the overlapping and transmittedsub packets, if it is assumed that the sub packet IDs corresponding tothe transmitted sub packets, for example, the bit combinations forrepresenting P1, P2, P3, and P4 are 00, 01, 10, and 11, the transmissionof the remaining bit combinations except for the bit combination forrepresenting the initial transmission start point, i.e., 00, may not beperformed in order, but may be performed in the order for heighteningthe coding gain (i.e., for reducing the occurrence of overlapping) orwith overlapping one another. Thus, as shown as (2) in FIG. 5A, it canbe confirmed that P1, P3, P1, etc., are successively transmitted.

Meanwhile, as shown in FIG. 4B, if it is assumed that the importance ofthe outputs X, Y0, and Y0′ of the turbo encoder 101 are higher than thatof Y1 and Y1′, X and (Y0+Y0′) are arranged in the front portion of theencoded packet generated by interleaving X, (Y0+Y0′), and (Y1+Y1″),respectively, and thus the front portion has a higher importance.

In this case, the transmitting end maps more transmission start pointson the front portion of the encoded packet when dividing the encodedpacket constructed by repeating the encoded packets into four parts.

At this time, even if the receiving end cannot receive a certain subpacket transmitted form the encoded packet, the probability that X, Y0,and Y0′ having a high importance are received can be higher, and theloss of the coding gain that may occur at equal intervals can bereduced.

FIG. 5B is a view illustrating transmission intervals of respective subpackets in case that start points in a encoded packet are divided atunequal intervals according to the present invention.

As shown as (2) in FIG. 5A, the transmission start points are divided atunequal intervals in the encoded packets, and the information of therespective sub packets may overlap each other according to theimportance of the information to be transmitted from the transmittingend.

In the same manner, as can be known through the overlapping andtransmitted sub packets, if it is assumed that the sub packet IDscorresponding to the transmitted sub packets, for example, the bitcombinations for representing P1, P2, P3, and P4 are 00, 01, 10, and 11,the transmission of the remaining bit combinations except for the bitcombination for representing the initial transmission start point, i.e.,00, may not be performed in order, but may be performed in the order forheightening the coding gain (i.e., for reducing the occurrence ofoverlapping) or with overlapping one another.

FIG. 6 is a view illustrating an encoded packet generated byregenerating the transmitted sub packets in a receiving end according tothe present invention.

Referring to FIG. 6, if the transmitting end transmits the respectivesub packets to the receiving end according to the above-described twomethods, the receiving end considers the sub packet ID transmitted fromthe transmitting end as a transmission start point indicator bit forinforming which position among P1, P2, P3, and P4 the presently sent subpacket starts to be transmitted from.

When the sub packet is received, the receiving end judges which positionthe received sub packet is transmitted from through the sub packetidentifier field on the control channel.

Then, the receiving end, using this positional information, generates anencoded packet by concatenating or combining the sequentiallytransmitted sub packets, and then decodes desired data from the encodedpacket.

Meanwhile, in transmitting the encoded packet composed of the subpackets of a variable length, the present invention proposes two methodsthat can discriminate whether the sub packet received in the receivingend is the sub packet that is transmitted from the initial transmissionstart point of the sub packet generated from certain information.

First, one method is that the transmitting end includes in the controlchannel control information of one bit for informing the receiving endwhether the transmitted sub packet is the sub packet of a new packettransmitted at the initial transmission start point of a certain packet.

Specifically, the transmitting end add a field that is calledNC_IND(NEW/CONTINUE Indication) to a control channel. At this time, thetransmitting end sets NC_IND to 0 for the sub packet transmitted fromthe initial transmission start point of the packet, and NC_IND to 1 forthe sub packet not transmitted from the initial transmission startpoint. The transmitting end toggles NC_IND to 1 if the presentlytransmitted sub packet is the sub packet of a new packet in a state thatNC_IND is successively set to 0. In the same manner, the transmittingend toggles NC_IND to 0 if the presently transmitted sub packet is thesub packet of a new packet in a state that NC_IND is successively set to1.

The receiving end judges that the transmitted sub packet is the subpacket transmitted from the initial transmission start point of theencoded packet if NC_IND is 0, while it judges that the transmitted subpacket is not the sub packet transmitted from the initial transmissionstart point if NC_IND is 1.

Also, if NC_IND having the state of 1 is received while NC_IND havingthe state of 0 is successively received, the receiving end judges thatthe presently received sub packet is the sub packet of a new packet. Inthis case, the receiving end performs a new independent decoding processwith respect to the presently received sub packet, but does not performthe concatenating/combining process with the previous sub packet. In thesame manner, if NC_IND having the state of 0 is received while NC_INDhaving the state of 1 is successively received, the receiving end judgesthat the presently received sub packet is the sub packet of a newpacket. In this case, the receiving end performs a new independentdecoding process with respect to the presently received sub packet, butdoes not perform the concatenating/combining process with the previoussub packet.

Second, the other method is that the transmitting end modifies thecontrol information on the transmission start point information of thetransmitted sub packet.

Here, a portion of the control information is used for representing thesub packet that is transmitted from the initial transmission startpoint. The remaining portion of the control information is used fortransmission of other transmission start point information that is notthe initial transmission start point. At this time, the transmissionposition of the sub packet is represented using three bits, which isillustrated in FIG. 7.

FIG. 7 is a view illustrating transmission intervals of respective subpackets of a variable length according to a hybrid automatic repeatrequest method according to the present invention.

The transmitting end informs the receiving end the transmission positionof the transmitted sub packet in the encoded packet and whether thetransmitted sub packet is the sub packet that is transmitted from theinitial transmission start point of the packet using three bits.Accordingly, P0(000) and P7(111) represent the initial transmissionstart point, and P1(001), P2(010), P3(011), P4(100), P5(101), andP6(110) represent positions of the remaining transmission start points.However, P0 is used as the control information of the sub packettransmitted from the initial transmission start point of the packet, andP7 is used as the control information of the successive sub packet ofthe previously transmitted sub packet even though it is the sub packettransmitted from the initial transmission start point of the packet.

Accordingly, the receiving end receives the 3-bit transmission positioninformation of the sub packet from the transmitting end, and if theposition information is P0(000), the receiving end judges thetransmitted sub packet to be the initially transmitted sub packet, whileif the position information is not P0(000), it judges the transmittedsub packet to be not the initially transmitted sub packet.

Though the above-described methods use the same control information, thefirst method provides four transmission positions of the sub packet, andthe second method provides seven transmission positions.

Second Embodiment

In the same manner, the second embodiment of the present inventionprovides a method capable of decoding received sub packets even if areceiving end fails to receive any one of the sub packets by fixingstart positions of the respective sub packets in a packet according to aspecified mapping method promised between a terminal and a basetransceiver system when transmitting the sub packets having a variablelength.

In the second embodiment of the present invention, however, a method ofdetermining the transmission position of the sub packet using the numberof coded symbols transmitted on the current sub packet is proposed.

Here, the encoder packet is generated according to the construction ofFIGS. 4A and 4B.

The transmission position of the sub packet generated as above isdetermined as follows.

If the size of the information bits on the encoded packet (i.e., theinput packet of the turbo encoder 101 in FIGS. 4A and 4B) and the lengthof the sub packet are determined, the size of the code symbol of the subpacket is also determined. Using this information, the transmissionposition of the presently transmitted sub packet is determined under theassumption that the previous sub packet has the same code symbol size asthe present sub packet.

The first sub packet whose sub packet identification (SPID) is 00 isalways transmitted from the initial position of the encoded packet(i.e., the output packet of the repetition block 103 in FIGS. 4A and 4B)to the receiving end. The code symbol size of the second sub packet isobtained using the encoder packet size corresponding to the second subpacket and the length information of the sub packet, and the second subpacket whose sub packet identification (SPID) is 01 is transmitted fromthe next position of the encoded packet under the assumption that thefirst sub packet is transmitted with the code symbol size correspondingto the second sub packet. The code symbol size of the third sub packetis obtained using the encoder packet size corresponding to the third subpacket and the length information of the sub packet, and the third subpacket whose sub packet identification (SPID) is 10 is transmitted fromthe next position of the encoded packet under the assumption that thefirst and second sub packets are transmitted with the code symbol sizecorresponding to the third sub packet. The code symbol size of thefourth sub packet is obtained using the encoded packet sizecorresponding to the fourth sub packet and the length information of thesub packet, and the third sub packet whose sub packet identification(SPID) is 11 is transmitted from the next position of the encoded packetunder the assumption that the first, second, and third sub packets aretransmitted with the code symbol size corresponding to the fourth subpacket. At this time, it is assumed that the SPIDs of 00, 01, 10, and 11are values transmitted in order. If the transmission start positions ofthe sub packets are determined as described above, the following effectscan be obtained. The case that the channel status is kept fixed at atime point when the respective sub packet is scheduled for transmission.If so, the length of the code symbol of the transmitted sub packet willbecome uniform. As a result, the transmission start position of thedetermined sub packet will be the same as that of the sequentialtransmitting method that can obtain the maximum coding gain under theassumption that the channel status is fixed.

Also, in case that the size of the code symbol to be transmitted throughthe respective sub packet is changed due to the change of the channelstatus during transmission of the respective sub packet, the sub packetID, i.e., the transmission start information of the sub packet, isdetermined so that the combining coding gain in the receiving end can bemade maximum using the above-described process. In this method, the subpacket ID is not transmitted in order, but is assumed to be a valuerandomly transmitted. Also, the transmitting end properly selects thesub packet ID at this time, so that the overlapping rate between the subpackets is lowered and thus the coding gain in the receiving end isheightened. Also, the sub packet IDs may overlap each other to heightenthe coding gain. This can be represented using an equation as follows.

First, it is defined that k is an index of a certain sub packet, N_(EP)is the number of bits of an encoded packet, N_(walsh,k) is the number of32-chip Walsh channels of the k-th sub packet, N_(slots,k) is the numberof 1.25 ms slots of the k-th sub packet, the ID of the k-th sub packetis SPID_(k), and m_(k) is a variable that varies according to themodulation technique of the sub packet. At this time, m_(k) is a valuethat is changed to 2, 3, and 4 in order according to the methods ofQPSK, 8-PSK, and QAM, and may be changed according to the additionalmodulation type. N_(EP), N_(walsh,k), and N_(slots/k) are valuesdetermined by the transmitting end (for example, base transceiversystem), and are transmitted to the receiving end (for example,terminal) through the packet data control channel.

Also, if it is assumed that bit sequences of the repetition block 103 inFIGS. 4A and 4B are numbered from 0, the number L_(k) of code symbolsselected among the bit sequences for a certain k-th sub packet isdetermined by the following equation 1.L _(k)=48*N _(walsh,k) *N _(slots,k) *m _(k)  [Equation 1]

Also, the starting of F_(k) of a certain sub packet in the encodedpacket corresponding to the determined number is determined by thefollowing equation 2. Here it is assumed that the coding rate of turboencoder is ⅕.F _(k)=(SPID _(k) *L _(k))mod(5N _(EP))  [Equation 2]

As is known from the equation 2, the position of the start point fortransmitting the present sub packet is selected among several startpositions made under the assumption that the length of the code symbolof the previously transmitted sub packet is equal to the length L_(k) ofthe code symbol transmitted from the present sub packet. At this time,the position of the start point to be actually transmitted can beselected in the transmitting end, and a method used for this selectionis to select the position so that the coding gain that can be obtainedthrough the sub packet combination in the receiving end is made maximum.The position of the start information selected as above is transmittedto the receiving end by the sub packet ID.

Table 1 as below represents a modulation type according to the length ofthe sub packet (i.e., the number of slots per sub packet) and the sizeof the code symbol in case that the length of the encoder packet (i.e.,data rate) is of 3072 bits, and the number of useable Walsh codes is 28.

TABLE 1 Slots per Sub Data Rate Packet (kbps) Modulation Code Symbols 8307.2 QPSK 21504 4 614.4 QPSK 10752 2 1228.8 QPSK 5376 1 2457.6 16-QAM5376

For example, in case that the length of the sub packet is 2, the numberof Walsh codes is 28, and 1.2288 Mcps chip is used, 48 modulationsymbols can be included in a slot, and thus 1344 (i.e., 48*28) chips aregenerated in a slot. Accordingly, two slots include 2688 chips, and thesize of the code symbols included in the chips is 5376 (i.e., 2*2688performed by the QPSK method).

FIGS. 8A and 8B are views illustrating an example of an AIR typetransmitting and restoring method according to the present invention.

In FIG. 8A, the length of the information bits on the encoder packet(i.e., the input packet of the turbo encoder 101 in FIGS. 4A and 4B) is3072 bits, and the number of useable Walsh codes is 28. The length ofthe first sub packet (i.e., the number of slots per sub packet) is 2,the length of the second sub packet is 4, the length of the third subpacket is 8, and the length of the fourth sub packet is 8.

Accordingly, a plurality of encoded packets, which include 15360 bits(3072*5), are generated as shown in FIGS. 4A and 4B, and thetransmission time points of the respective sub packets in the encodedpackets are determined as follows.

That is, the first sub packet “00” is transmitted from the first of theencoded packet.

The receiving end successfully performs the decoding of one sub packet,and transmits an acknowledgment (ACK) to the transmitting end. Then, thetransmitting end does not transmit any more sub packets.

However, if the receiving end fails to decode, it transmits anon-acknowledgment (NACK) to the transmitting end. Then, thetransmitting end transmits the sub packet having the next SPID.

Accordingly, the code symbol size of the second sub packet is 10752 at atime point when the second sub packet “01” is transmitted, and if it isassumed that the previously transmitted sub packet has the code symbolsize obtained in the present sub packet, the second sub packet istransmitted from the 10752nd position among the code symbols of theencoded packet.

In the same manner, the code symbol size of the third sub packet is21504 at a time point when the third sub packet “10” is transmitted, andif it is assumed that the previously transmitted sub packet has the codesymbol size obtained in the present sub packet, the third sub packet istransmitted from the 12288th (i.e., 21504*2−15360*2) position among thecode symbols of the encoded packet.

The code symbol size of the fourth sub packet is 21504 at a time pointwhen the fourth sub packet “11” is transmitted, and if it is assumedthat the previously transmitted sub packet has the code symbol sizeobtained in the present sub packet, the fourth sub packet is transmittedfrom the 3072nd (i.e., 21504*3−15360*4) position among the code symbolsof the encoded packet.

According to the above-described process, the receiving end, as shown inFIG. 8B, regenerates the encoded packets using the received sub packets,and decodes the regenerated encoded packets.

FIGS. 9A and 9B are views illustrating another example of an AIR typetransmitting and restoring method according to the present invention.

In FIG. 9A, the length of the encoder packet is 3072 bits, and thenumber of useable Walsh codes is 28. The length of all the sub packetsis 4 since a modulation and coding scheme level is not changed.

Accordingly, a plurality of encoder packets, which include 15360 bits,are generated as shown in FIGS. 4A and 4B, and the transmission timepoints of the respective sub packets in the encoded packets aredetermined as follows. At this time, the size of the code symbols of therespective sub packets is 10752.

That is, the first sub packet “00” is transmitted from the first of theencoded packet.

The receiving end successfully performs the decoding of one sub packet,and transmits an ACK to the transmitting end. Then, the transmitting enddoes not transmit any more sub packets.

However, if the receiving end fails to decode, it transmits a NACK tothe transmitting end. Then, the transmitting end transmits the subpacket having the next SPID.

Accordingly, the code symbol size of the second sub packet is 10752 at atime point when the second sub packet “01” is transmitted, and thus thesecond sub packet is transmitted from the 10752nd (i.e.,10752*1−15360*0) position among the code symbols of the encoded packet.

In the same manner, the code symbol size of the third sub packet is10752 at a time point when the third sub packet “10” is transmitted, andthus the third sub packet is transmitted from the 6144th (i.e.,10752*2−15360*1) position among the code symbols of the encoded packet.

The code symbol size of the fourth sub packet is 10752 at a time pointwhen the fourth sub packet “11” is transmitted, and thus the fourth subpacket is transmitted from the 1536th (i.e., 10752*3−15360*2) positionamong the code symbols of the encoded packet.

According to the above-described process, the receiving end, as shown inFIG. 9B, regenerates the encoded packets using the received sub packets,and decodes the regenerated encoded packets.

That is, the receiving end, that received the sub packets, concatenatesor combines at least one sub packet previously transmitted with thereceived sub packet according to the number of code symbols of thereceived sub packet.

As shown in FIG. 9B, it can be confirmed that another example accordingto the present invention performs the encoded packet transmission in thesame manner as the sequential transmitting method.

As described above, the present invention provides the followingeffects.

First, in case that the sub packets have a variable length, thereceiving end can regenerate the sub packets into one packet and performthe decoding even though any sub packet is missing.

Second, in case of transmitting the sub packets having a variablelength, the receiving end can perform the decoding of the encoded packetthrough the next sub packet even though it cannot receive the controlchannel, and thus the power consumption occurring due to the controlchannel can be reduced.

Third, the start points of the sub packets are positioned at unequalintervals, and thus the loss of the coding gain occurring at the startpoints of equal intervals can be minimized.

Fourth, the receiving end can judge whether the transmitted sub packetis the initially transmitted sub packet of the packet, and thus thereceiving end can perform a proper operation.

Fifth, since the fixed-position transmitting method is used, thereceiving end can successfully combine the received sub packets even ifthe sub packet is lost during performing the sequential transmittingmethod, and improve the reliability of ACK/NACK.

Sixth, since the size of the code symbol is not changed in case that theMSC level per sub packet is not changed, the transmission is performedin the same manner as the sequential transmitting method, and asufficient coding gain according to the HARQ method can be obtained,being different from the fixed-position transmitting method.

It will be apparent to those skilled in the art than variousmodifications and variations can be made in the present invention. Thus,it is intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method of transmitting a data packet from a transmitter to areceiver in a packet data communication system using hybrid automaticrepeat request, the method comprising: forming an encoded data packetgenerated by encoding information to be transmitted at the transmitter;generating at least one sub packet from the encoded data packet at thetransmitter, each of the at least one sub packet having a sub packetidentifier; and transmitting one of the at least one sub packet and aspecific indicator to the receiver, wherein the specific indicator istransmitted separately from the one of the at least one sub packet andindicates whether one of the at least one sub packet a sub packet of anewly encoded data packet or a retransmitted sub packet of a previouslyencoded data packet.
 2. The method of claim 1, wherein the sub packetidentifier has a 2-bit length and the specific indicator has a 1-bitlength.
 3. The method of claim 2, wherein the transmitter toggles thespecific indicator if the one of the at least one sub packet is the subpacket of the newly encoded data packet.
 4. The method of claim 1,wherein the specific indicator is transmitted to the receiver via acontrol channel.
 5. A method of receiving at least one sub packet from atransmitter in a packet data communication system using hybrid automaticrepeat request, the method comprising: receiving a sub packet and aspecific indicator from the transmitter at the receiver, the sub packethaving a sub packet identifier; and decoding the sub packet receivedfrom the transmitter at the receiver using at least the sub racketidentifier or the specific indicator, wherein the specific indicator isreceived separately from the sub packet and indicates whether sub packetreceived from the transmitter is a sub packet of a newly encoded datapacket or a retransmitted sub packet of a previously received datapacket.
 6. The method of claim 5, wherein the sub packet identifier hasa 2-bit length and the specific indicator has a 1-bit length.
 7. Themethod of claim 6, wherein the receiver determines the sub packetreceived from the transmitter is the sub packet of the newly encodeddata packet if the specific indicator having the 1 bit length istoggled.
 8. The method of claim 5, wherein the specific indicator isreceived from the transmitter via a control channel.